1. Field of the Invention
The invention pertains to systems and methods for impact welding by magnetic implosion.
2. Description of the Prior Art
Impact welding is a known technique. By this method, a ballistic work piece is caused to collide at a velocity of 350 meters per second and an angle of 8-12 degrees with a part or parts to be welded. The joinder is apparently the result of a jetting action between the colliding surfaces which is such that it cleans the surfaces, thus providing the capability of a joinder through the well-known interaction of smooth and clean surfaces. In many applications, impact welding is accomplished through the technique known as explosive welding, whereby the appropriate collision velocity is attained by means of a chemical explosion which hurls the ballistic work piece against the parts to be joined. This technique is used in various applications, such as pipe welding and the like; however, it has obvious disadvantages in its requirement of high skill on the part of the welder, its inescapable hazard, and the noise produced by the technique, among other disadvantages.
Other methods have been utilized in order to achieve the required collision velocity and angle for impact welding. Among these is the use of magnetic implosion to thrust the ballistic work piece against the work piece to be welded. Under this technique, a plurality of wires, known as a driving coil, are affixed to the ballistic work piece and are connected to a power source, such as a capacitor bank. The required collision velocity is achieved by means of a magnetic implosion which results from a surge of current through the power source which causes implosion through the mutual repulsion of the work piece and the components of the driving coil. This technique has been used in particular to weld the ends of nuclear fuel rods, and has also found application in other contexts in which the diameters of the parts to be joined are small. Extension of this technique of magnetic implosion to parts of larger dimensions has proved unfeasible because of the inefficiency of power utilization therein. Investigation has disclosed that normally less than one percent of the power provided by the power source is actually utilized in producing the magnetic implosion. For this reason, the size of the capacitor bank would increase quadratically, according to investigation, with an increase in the diameter of the parts to be joined and, consequently, of the ballistic work piece. The increase in size and electrical requirements of the power source with increasing size of the work piece and ballistic work piece is such that application of the technique of impact welding by magnetic implosion has been limited to contexts in which the diameters of the ballistic work piece and work piece are relatively small, as in the example of nuclear fuel rods. Specific examples of existing apparatus and methods relating to impact welding by magnetic implosion are U.S. Pat. Nos. 2,976,901 and 3,195,335, together with an article appearing the Journal of Applied Physics, Volume 50, November, 1979, No. 11, Part 2, entitled, "Measurements of a 70 T Pulsed Magnetic System with Long Operational Life."
Therefore, there has been a felt but unfulfilled need for a system and method for accomplishing impact welding by magnetic implosion operating at efficiencies such that such welding may be applied to work pieces of substantial diameter, such as those found in oil pipelines.